A separations problem which has required and received considerable attention is that of separating unsaturated aliphatic hydrocarbons such as olefins from close boiling and difficulty separable saturated aliphatic hydrocarbons such as paraffins. Many processes have been proposed for such separations including liquid-liquid extraction, extractive distillation, as well as complex formation. With respect to complex formation, various complexing reagents have been described in the prior art. However, difficulties exist with the previously known systems. For example, aqueous systems involving Cu(I) salts and ammonia or ammonium are corrosive and lack necessary long term stability. Non-aqueous Cu(I) solutions using a pyridine solvent have proven difficult to handle due to the solvent and require large scale systems because the reagent is in the form of a slurry in the solvent. Solvent losses and solvent recovery problems have also been experienced with the non-aqueous systems. Cu(I) sulfonic acid reagents have proven too viscous for easy handling; furthermore the strong heats of absorption of these salts for olefins render the decomplexation difficult. Finally, Cu(I) salt/Lewis acid systems disclosed in the prior art have evidenced solubility problems and solvent alkylation problems.
There exists therefore, the need for a complexing reagent which has a high olefin complexing capacity while providing for easy desorption of the olefin, has a high solubility in an inert solvent, has a favorable viscosity, is relatively stable, gives few side reactions during the complexing process, and can be prepared from cheap starting materials.
It is an object of this invention to provide complexing agents for separation of olefins from paraffins which exhibit good olefin complexing capacity and easy reversibility, and are soluble in an inert solvent.
It is also an object of this invention to provide a method for preparing such complexing reagents from relatively inexpensive starting materials.
It is also an object of this invention to provide a method for separating olefins from a mixture of olefins and paraffins by using the aforementioned complexing reagents.